[vtkusers] Glyph coloring

[Gib Bogle]

Ahah!  That works.  I get the array pointer with
vtkSmartPointer<vtkDataArray> colors = input->GetPointData()->GetScalars();

I'm seeing some odd with the color, which I didn't see when using actors for the 
individual tiles.  I set the color to be off-white {0.9, 0.9, 0.5}, supposed to 
be bone color.  The tiles look OK when viewed at right angles, but as they are 
rotated the color shifts toward a pale mauve.  Could this be related to the 
properties I'm using?  I don't change the default scene lighting, but I set 
glactor properties thus:
   glactor->GetProperty()->SetAmbient(0.5);
   glactor->GetProperty()->SetDiffuse(0.2);
   glactor->GetProperty()->SetSpecular(0.5);


On 26/11/2010 4:22 p.m., David Gobbi wrote:
> It should be possible to modify the scalars the same way as the points:
>
> points->SetPoint(idx, point);
> colors->SetTupleValue(idx, color);
> glypher->Modified();
>
> The vtkCellArray isn't necessary (but somehow polydata with no cells goes
> against my sense of aesthetics).
>
>    David
>
> On Thu, Nov 25, 2010 at 7:07 PM, Gib Bogle <g.bogle at auckland.ac.nz
> <mailto:g.bogle at auckland.ac.nz>> wrote:
>
>     It turns out there was a difference between what I was doing and the wiki
>     example code, one of those seemingly insignificant details that are actually
>     important.
>
>     I had
>       glypher->SetScaleFactor(1.0);
>     and the wiki code has
>       glypher->ScalingOff();
>     With that change it works (although I don't know why).
>
>     I have a final (I hope!) question.  I now want to selectively change the
>     color of glyphs.  I know how to change the position of the point indexed by idx:
>       points->SetPoint(idx,x,y,z);
>       glypher->Modified();
>
>     Presumably something very similar is needed to change the color of this
>     glyph, but I don't know how to access the array that holds the colors, which
>     was initialized with:
>       input->GetPointData()->SetScalars(colors);
>
>     Can someone help me over this last hurdle?
>
>
>
>     On 26/11/2010 12:42 p.m., Gib Bogle wrote:
>
>         I've been trying to follow David Gobbi's suggestion about coloring the
>         glyphs
>         that I am now using to render my squares with. The hints he provided
>         were not
>         enough for me to get it working, so I hunted around and found the wiki
>         example
>         http://www.itk.org/Wiki/VTK/Examples/Cxx/Visualization/ColorGlyphs
>         This works fine, so I thought I could just follow the same path. It
>         doesn't work
>         for me, and I'm guessing that it's because I'm using a vtkPolyData that
>         contains
>         both vtkPoints and vtkCellArray. David advised me to use
>         input->GetPointData()->AddArray(...)
>         but I couldn't see how to implement this. My code is shown below. What am I
>         missing? (This code doesn't display the squares at all, unless I comment out
>         input->GetPointData()->SetScalars(colors).)
>         I apologize for the ignorance I'm displaying - I don't understand why it's
>         necessary to use the vtkCellArray, for example.
>
>         points = vtkSmartPointer<vtkPoints>::New();
>         vtkSmartPointer<vtkCellArray> dummycells =
>         vtkSmartPointer<vtkCellArray>::New();
>         points->SetNumberOfPoints(npos); // number of squares
>         dummycells->InsertNextCell(npos);
>         colors = vtkSmartPointer<vtkUnsignedCharArray>::New();
>         colors->SetName("colors");
>         colors->SetNumberOfComponents(3);
>         unsigned char g[3] = {0,255,0};
>         for (int ipos=0; ipos<npos; ipos++) {
>         points->SetPoint(ipos, x, y, z);
>         dummycells->InsertCellPoint(ipos);
>         colors->InsertNextTupleValue(g);
>         }
>         input = vtkSmartPointer<vtkPolyData>::New();
>         input->SetPoints(points);
>         input->SetVerts(dummycells);
>         input->GetPointData()->SetScalars(colors);
>         glypher = vtkSmartPointer<vtkGlyph3D>::New();
>         glypher->SetInput(input);
>         glypher->SetSource(polygonPolyData);
>         glypher->SetScaleFactor(1.0);
>         glypher->SetColorModeToColorByScalar();
>         // glypher->SetInputArrayToProcess(3, 0, 0, 0, "colors");
>         glypher->Update();
>         squareMapper = vtkPolyDataMapper::New();
>         squareMapper->SetInputConnection(glypher->GetOutputPort());
>         glactor = vtkActor::New();
>         glactor->SetMapper(squareMapper);
>         glactor->GetProperty()->SetAmbient(0.5);
>         glactor->GetProperty()->SetDiffuse(0.2);
>         glactor->GetProperty()->SetSpecular(0.5);
>         ren->AddActor(glactor);
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